Sydney | As government representatives gather at the COP29 international climate summit in Azerbaijan, the impact of climate change on young people's mental health needs to be an urgent priority.

As psychiatrists working with children and adolescents, we're so concerned that we're sharing our research at the summit on the link between higher temperatures and suicidal thoughts and behaviours.

Our recent study shows young people are more likely to present at the emergency department for suicidal thoughts and behaviours in hotter weather.

Here's what we found and why one of us (Cybele Dey) is presenting our findings at COP29.

Mental health is getting worse

Young people's mental health is getting worse in Australia and across the world. There is growing evidence inadequate action on climate change is contributing. But it goes beyond young people worrying about how climate change will affect their future.

Climate change is here, and its effects are already damaging young people's mental health. Extreme weather events – such as Australia's devastating Black Summer bushfires in 2019 and storms and floods since – disrupt children's schooling, force displacement and cause trauma, anxiety and stress.

Our study is showing another, less talked about dimension.

Suicidal behaviour risk increases with hotter weather

Small increases in average temperatures can mean a large rise in the number of hot days each year. In 2019, for example, Australia had 33 days averaging over 39°C – more than the total number of the preceding 59 years.

While studies have shown a link between hot weather and adult suicidal thoughts and behaviour, the issue is under-researched among young people.

Given suicide is a major health issue for young people – it is the leading cause of death for Australians aged 15-24 – we wanted to investigate this link.

Our recent study looked at all emergency department presentations in New South Wales for suicidal thoughts and behaviour by people aged 12-24, during the warmer months (November to March) between January 2012 and December 2019.

We looked at these warmer months to focus on daily average temperature and heatwaves, rather than compare between seasons.

We found for every 1°C rise in average daily temperature, emergency department visits by young people for suicidal thoughts and behaviour increased by 1.3%. For example, presentations were 11% higher on days averaging 30°C, compared to days with an average 21.9°C. The risks also increased significantly even on days that were average temperature (not extreme heat), when compared to mild, cool days during the warmer months.

A study like this can only show an association between heat and suicidal thoughts and behaviour, rather than a direct cause. But the relationship was very strong. This means there was a steady and predictable worsening as ambient temperatures rose.

We also analysed heatwaves, meaning three or more very hot days in a row. Interestingly, presentations increased as much on the first hot day as on later days of a heatwave. That means each single hot day is as bad as another.

Heat and inequality

Our study also found young people in regions with some of Australia's most disadvantaged suburbs had a higher risk of presenting at emergency for suicidal thoughts and behaviours than those in more advantaged areas, even at the same temperature.

This is significant because previous research has shown socioeconomic disadvantage in itself does not increase risk for suicidal thoughts and behaviour in young people.

But disadvantage can mean people are more vulnerable to the harms of hot weather. For example, this could be through lack of cool shelter or inability to pay for air conditioning or other cooling, as well as a lack of transport and access to trees and water.

Complex interactions for mental health

Understanding mental health impacts of climate change means examining complex interactions between multiple factors, and over time. Simple, linear “cause and effect” models do not capture this.

Anxiety about climate change does also play a role in young people's mental health. But children and teenagers who show high levels of distress may be expressing a healthy response to an unhealthy reality, rather than a mental disorder.

Inadequate action and dismissive responses by those in authority, including governments, worsens their distress.

What we'll be telling COP29

At COP29, leaders must understand youth mental health is already seriously affected by insufficient action on climate change, from increasing extreme weather, heat, forced migration and disruption to school, work and health care.

High-income countries such as Australia must rapidly and equitably transition off fossil fuels, including gas, in line with scientific evidence and leadership by our Pacific neighbours, to reduce climate distress now.

Our research suggests this may help reduce youth suicide and suicidal thoughts and behaviours, and improve mental health more broadly.

How can we adapt?

If we are to adapt to climate change, we need to prepare the mental health system at national, state and local levels.

Public health messaging about heat should also consider the risks of single hot days, not just heatwaves. It should target young people and include information about mental health as well as physical health.

This information should also be part of how health professionals are trained. The current National Health and Climate Strategy includes two recommendations on mental health, focusing on community resilience and building a workforce trained in climate change and mental health. These need to go from policy into action.

Sensible public health measures – such as improving rental standards and equipping bus shelters for extreme heat – are needed now. We must plan for increases in mental health-care needs, including access to primary mental health care and evidence-based, local and culturally-appropriate treatments for children and young people.